Pain is a frequent symptom in the intensive care unit (ICU). Critical ill patients are often intubated and sedated which makes self-evaluation of pain impossible.

Pupillary dilatation is a reflex directly related to stimuli such as pain, which can be measured by quantitative pupillometry.

Several studies in ICU showed a significant relationship between pupillary diameter variation and pain.

The nociception level index (NOL-index) is a recent noninvasive and continuous monitoring of pain essentially used in operating room.

The aim of this study is to evaluate the pupillometry and NOL index in critical ill patients in sedated patients under mechanical ventilation during the mobilization plus toilet (described in literature as not painful procedure) and tracheal suctioning (described as a painful procedure)

Pain will be evaluated via i) pupillometry with 3 successive measurements ii) Behaviour Pain Scale (BPS) and Critical Care Pain Observation Tool (CPOT) score evaluated by an investigator (physician) iii) evolution of physiological parameters (ie heart rate, blood pressure, respiratory rate) iv) Nociception level index (NOL-index).

The evaluation times will be 5 minutes before care procedures (mobilization plus toilet and tracheal suctioning), during the procedures (with the worst value recorded) and 5 minutes after the procedures.

The procedures are:

• A mobilization and toilet of the patient: a priori, not a very painful procedure. The pain will be evaluated every 5 minutes during the toilet.
• Tracheal suctioning: a procedure known to be painful. The painful will be evaluated just at the end of tracheal suctioning (once the tracheal suctioning catheter is removed from the endotracheal intubation).

Inclusion Criteria:

• older than18 years old
• Under invasive mechanical ventilation
• Sedated with i) a Richmond Agitation Sedation Scale (RASS) : ≥ -4 and <1, ii) being unable to evaluate their pain by a visual numeric scale

Exclusion Criteria:

• Ophthalmological diseases which could modify the pupillometric parameters
• Neurological diseases (damage of nerve III, intracranial hypertension, stroke)
• Admitted in ICU after resuscitated cardiac arrest
• Drugs that inhibit the effect of the sympathetic system (clonidine, dexmedetomidine)
• Patient under Veno-Arterial Extracorporeal Membrane Oxygenation (VA-ECMO)
• Patient treated by a neuromuscular blockade
• A do-not resuscitate order
• Major hemodynamic instability prohibiting planned care procedures